The invention relates to an arrangement for the protection of electronic functional units and/or functional groups, such as circuitries, circuit components, consumers, sensors, and the like, from disturbance variables like electromagnetic radiation, capacitive coupling, vibrations, and the like. In such electronic functional units and/or functional groups of automotive control systems, such as anti-lock brake systems (ABS), traction control systems (TCS), and particularly systems for driving stability control (ESP), the detected measuring quantities must be recorded and evaluated disturbance-free, for the measuring quantities recorded and evaluated by the functional units and/or functional groups influence or initiate safety-relevant brake events which automatically change the driving behavior of an automotive vehicle. It is a known fact that electronic functional units and/or groups used in automotive control systems include measurement recorders with highly sensitive low-frequency input stages as well as digital evaluation circuitries which are operated at a given, stable cycle of high frequency. Here, as known, disturbance signals appear at the basic frequency of the working cycle which, though narrow-banded, however can assume high amplitudes. Further on, disturbance coupling can occur due to the shift of potential of a circuitry-internal shared reference conductor to ground (ground loops) and also influences on the electromagnetic tolerance of the sensitive electronic functional units and/or groups caused by mobile phones and/or other emitters if these are active with a high output power in immediate vicinity of the functional units and/or groups. Beside these electric disturbance quantities, mechanical disturbance quantities, such as vibrations, temperature influences, torsions, and the like, influence the functional units and/or groups.
The invention is therefore based on the objective to create an arrangement for disturbance-free recording, evaluation, and transmission of safety-relevant measuring quantities.
This objective is achieved, according to the invention, by means of the features of claim 1.
The invention is based on the basic idea of a division of the functional units and/or groups into partial units and/or groups with different sensitivity regarding the disturbance quantities and of an assignment of different screenings according to the sensitivity of the partial units and/or groups, wherein at least two of the screenings complete each other to a screening with a higher efficiency degree or factor, respectively. By means of the division of the functional units and/or groups into partial units and/or groups with different sensitivity regarding the disturbance quantities, it is advantageously possible to design the screening from mechanical and electric disturbance quantities in dependence on the sensitivity of the partial units and/or groups. Here, it is provided that the screening assigned to the partial units and/or groups is identical in structure so that the screenings complete each other additively in their effect to a higher efficiency degree or factor. The invention is based on the insight that, through a stepped screening having an inner area with a high screening level and an outer area with a lower screening level and being built of a gradation of screening through always identical screening of screened areas, under assignment of the partial units and/or groups and/or of the functional units and/or groups dependent on the sensitivity regarding disturbance quantities, safety-relevant measuring quantities can be recorded, evaluated, and transmitted disturbance-free.
All partial units and/or groups with different sensitivities are arranged in separate housings, respectively. By means of the arrangement in separate housings, on the one hand, a mechanical protection of the partial units and/or groups is obtained, and on the other hand, each housing can be provided with an identical or different screening. Further on, partial units and/or groups arranged in separate housings can easily be assembled and manufactured.
Advantageously, the partial units and/or groups are connected by lines guided through the housing and connected capacitively to the housing via capacitors. The separate housings screened in this manner short-circuit high-frequency disturbance pulses with the ground, so that disturbance couplings and influences on electromagnetic tolerance are prevented. There is no galvanic contact between the housings and the environment of the circuitry.
Due to the fact that a first housing accommodating the most sensitive partial unit and/or group is surrounded by at least one further housing in which another partial unit and/or group with a lesser sensitivity is arranged, the screenings of the individual separate housings complete each other additively to a higher total efficiency degree of factor, respectively, where the screening by the outermost end housing provides the least, and the screening by the innermost housing, which is surrounded by all other screened housings, provides the highest efficiency degree. The arrangement thus consists of several electronic partial units and/or groups which are separated by cascade-like enclosing housings. Here, the inner housing, encased by the outer one, contains electronic partial units and/or groups that react more sensitively to electromagnetic radiation or capacitive couplings, respectively, than the partial units and/or groups that are arranged within the space of the encasing housing.
According to an advantageous further embodiment, on an end housing surrounding all other housings, a plug-in element is provided to which all lines of the partial units and/or groups arranged at the end housing are connected. In the end housing, beside the plug-in element (connection plug), also elements are integrated for mechanically fastening the complete functional unit and/or group to a consumer, e.g. for mechanically fastening to the vehicle chassis of an automotive vehicle.
Due to the fact that the lines guided to the plug-in element are each connected, via a capacitor, with a connection element which via a capacitor is connected to the end housing, there is no galvanic contact between this housing and the electric environment of the circuitry. A simple module is attained.
Preferably, the electronic functional units and/or functional groups are designed as a closed arrangement where multiple measuring quantities are recorded at a shared measuring location, are locally digitized and, if applicable, pre-processed regarding the signal, and then, via an appropriate interface, in particular a bus, are transmitted to connected participants of this interface, e.g. a control unit for ESP (ESPxe2x80x94Electronic Stability Program). To this end, a yaw rate sensor with a high sensitivity to disturbance quantities is arranged in the first housing as a partial unit and/or group. In general, such yaw rate sensors possess a movable mechanical structure which comprises an electrical-mechanical converter excited with a periodical oscillation. If this sensor encounters a turn around an axis perpendicular to the excited oscillation, the movement of the oscillation results in a Coriolis force which is proportional to the measuring quantity, i.e. the angular velocity. Through the Coriolis force, a second oscillation, perpendicular to the excited oscillation is excited in a mechanical-to-electrical converter. This second oscillation can be recorded by means of different measuring methods, where the recorded quantity serves as a measure for the rate of rotation acting on the yaw rate sensor.
According to a preferred embodiment, the partial unit and/or group arranged in a second housing surrounding the first housing is a lateral and/or longitudinal accelerometer and signal processing steps for the lateral and/or longitudinal accelerometer and for the yaw rate sensor. This partial unit and/or group has a lesser sensitivity to the previously mentioned disturbance quantities, for their signal amplitudes are greater.
In a further advantageous embodiment of the invention, the partial unit and/or group arranged in a third housing surrounding the first and the second housing is a network, in particular a signal processor, and a bus controller. The network, that digitally processes the signals coming from the sensors and signal processing steps and formats them for a bus connection CAN (Controller Area Network), is arranged on a circuit board (assembly unit).
Basically, the invention pursues the principle that always one partial unit of a functional unit and/or group screened by a housing is, together with a partial unit not screened by this housing, surrounded by a housing covering both partial units, and this screening principle is continued in a cascade-like manner until a demanded total screening effect is achieved.
Preferably, there is galvanic connection of the housings to the partial units of a functional unit and/or group, but always a capacitive connection between every housing and the electric lines into this housing. Only the connections C3 and C7 can be designed as an exception of the strict galvanic separation, which, according to an embodiment, build, as a bridge, i.e. without a capacitor, a direct connection between the respective housing and ground. By means of this design, the screening can be enhanced in certain cases as empirical studies showed.
The housings are connected with each other via vibration-damping coupling elements which likewise complete each other in their total effect to a total damping with a higher degree of efficiency than each individual damping of every separate housing.
The preferably metallic or electrically conducting housings, respectively, are screwed in a galvanically conducting way onto the vehicle chassis, where, due to the cascade-like screening, no impermissible electric or high-frequency disturbance influences appear within the screened housings which can falsify the safety-relevant measuring quantities. The direct metallic contact allows as well for a good thermal abduction of the housings among each other and thus of the end housing to the vehicle chassis. At the same time, the metallic housing provides for a sufficient torsion stiffness which is necessary in order to measure the yaw rate and the lateral and/or longitudinal acceleration with sufficient precision. Due to the vibration-damping measure, a falsification of the output signal of the yaw rate sensor caused by internal acoustical resonance phenomena or by body sound influences via the vehicle chassis is prevented.